The primary focus of this project is to study the thyroid-specific proteins that are the target of the immune system in Graves' disease and Hashimoto's thyroiditis. These proteins include the TSH receptor, the thyroid "microsomal" antigen, and other autoimmune thyroid disease-related antigens (ATRA's). The goal is to expand our information on the identity, character and regulation of expression of these "auto"-antigens. Specifically it is proposed to perform the following studies: 1. Molecular cloning of the TSH receptor. a) Isolation of a full-length cDNA for HHB, the putative TSH receptor gene, from a new human thyroid cDNA library that will be constructed. The nucleotide and derived primary amino acid sequence of HHB will be determined. b) Study of the specificity of the cell-free translated HHB protein with a panel of antisera from patients with autoimmune thyroid disease. c) Expression of the full-length HHB cDNA in non-thyroid eukaryotic cells. d) If HHB turns out not to be the TSH receptor, we will select new clones or use clones obtained by other laboratories to perform the studies described above. 2. Studies on the cloned microsomal antigen/thyroid peroxidase (TPO) a) Identification of the B-cell epitope(s) on TPO in Hashimoto's thyroiditis. b) Identification of the T-cell epitope(s) in Hashimoto's thyroiditis, and the generation of TPO specific T-cell clones. c) Development of sensitive and specific assays for the microsomal/TPO antigen using recombinant antigen. 3. Studies on ATRA 1 and other automimmune thyroid disease-related (ATRA) antigens that may be recognized in future studies. a) Isolation of a full-length cDNA clone for the recently identified ATRA 1, and determination of its nucleotide and derived primary amino acid sequence. b) Study of the specificity of the ATRA 1 protein by immunoprecipitation of the cell-free translated protein with a panel of antisera from patients with autoimmune thyroid disease. c) Expression of the ATRA 1 protein in non-thyroid eukaryotic cells. d) Isolation of ATRA 1 genomic clones in order to study the promoter region of this gene and its potential regulation by TSH.